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Layered double hydroxides (LDHs) are nanomaterials with interesting properties finding applications in many fields, such as catalysis, environmental chemistry, and pharmaceuticals. They are anionic clays with positively charged layers and anions within the layers to reach neutrality. Their properties are defined by both composition and morphology. The composition can be tuned by exchanging the interlayer anion. The far more stable, common, and highly prevalent among natural LDHs is the carbonate anion thanks to its double negative charge. To adapt the properties of LDHs for technological applications, the challenge is to exchange the carbonate with the functionalizing monovalent anions in an effective and cheap way. In this study, the exchange of carbonate with nitrate ions is studied by in situ X-ray powder diffraction (XRPD). The exchange is carried out by a liquid-assisted grinding approach, inserting the mechanically ground dry sample in a capillary and then wetting it with a drop of nitric acid, while measuring the XRPD pattern. The kinetics of the process was investigated by the Avrami-Erofe'ev method; the reaction mechanism was determined using the advancing interface model and by analyzing the XRD peak shapes, which evidentiate changes in the crystallinity during the reaction. The reaction starts from the faces perpendicular to the layers and occurs along the channels, increasingly limited by diffusion when approaching the internal part of the crystals. [ABSTRACT FROM AUTHOR]

The crystal structure of sodium naphthalene 2-sulfonate (Na2-NS) is reported. This compound raised the attention as a pollutant, being widely used in industry, and its intercalation in inorganic matrices, such as layered double hydroxides (LDH), could be a suitable removal strategy. The crystal structure of the title compound, despite its simplicity, is not known in the literature, so we looked for a strategy to grow crystals suitable for a single crystal study. Although many attempts were made to recrystallize it, Na2-NS grows in bunches of very thin laminae, with a high degree of mosaicity and intergrowth, explaining the absence of a reported crystal structure. The crystal structure shows layers of Na+ cations with the organic part arranged in between. The crystals grow easily in the layer plane, whilst the growth perpendicular to the layers is driven by weak non-bonding interaction and thus unfavored. The crystal packing features were related to the density of charges in the cationic layer with respect to the size of the anion. By comparing the crystal structures of 2-NS salts with different cations, and with or without an amino substituent in different positions, it was possible to find the relationship between the density of the positive charges and the deepness of interdigitation of the 2-NS moieties. We exploited this information to shed light on the structural features of 2-NS and related compounds intercalated into LDH. The X-ray powder diffraction pattern of 2-NS intercalated LDH (V. Toson, E. Conterosito, L. Palin, et al. Facile intercalation of organic molecules into hydrotalcites by liquid-assisted grinding: yield optimization by a chemometric approach. Cryst. Growth Des. 2015, 15, 5368) resulted consistent with a crystal packing characterized by the partial interdigitation of the 2-NS anions. [ABSTRACT FROM AUTHOR]

Abstract: The study of a series of cis-[APtCl2] complexes (A=ethylenediamine, en, methylated at different positions) was carried out to evaluate the effect of different methyl substitutions on the cytotoxic properties of the resulting derivatives. As expected, differentially methylated complexes were found to differ widely in their cytotoxic effects on human cultured ovarian carcinoma cells (A2780). Molecular mechanics (MM) calculations have been performed to assess the relationship between differential diamine methylation and the repulsive energy of the corresponding complexes when interacting with DNA. Compounds that bind DNA at high energetic cost relative to cisplatin, due to the steric hindrance of additional methyl groups, have shown high values for IC50 (concentration inhibiting tumour cell growth by 50%). Semi-quantitative analyses with a DNA electrochemical biosensor confirm that the interaction between cis-[APtCl2] complexes and ds-DNA deposed onto the electrode is stronger for the non-methylated derivative with respect to the fully methylated congener. In addition, MM calculations were used to investigate the interactions between DNA and cis-[(P-L-A)PtCl2] complexes [A=en group linked to an antiestrogen-like pharmacophore, P, via a –(CH2)n– spacer (n =2, 4, 6, 8 and 10), L]. [Copyright &y& Elsevier]

Abstract: The structure of the [Os(bpy)2(CO)Cl]+Otf– complex (where bpy=2,2′-bipyridine and Otf– =triflate, CF3SO3 –) has been solved by single crystal X-ray diffraction analysis and the NMR technique has been employed for the characterization of the complex in solution. Theoretical calculations have been performed to unravel the structural disorder found in the solid state and for the characterization of the geometric and energetic features of the complex in apolar solution. This study is part of our investigation of Os(bpy)2(CO) complexes and in this paper we also intend to investigate the effect of different anions on the solid and solution properties of the [Os(bpy)2(CO)Cl]+ cation. To cite this article: G. Croce et al., C. R. Chimie 8 (2005) . [Copyright &y& Elsevier]

The high X-ray flux available at the European Synchrotron Radiation Facility (ESRF), combined with the use of a suitably designed area detector setup, allowed us to follow in real time the structural changes occurring during the template burning processes inside TS-1 and Fe-silicalite MFI zeolites with a X-ray powder diffraction technique (XRPD). Rietveld analysis of the XRPD patterns collected in the 350-1000 K interval, integrated each 15 K, yields to the determination of the template overall occupancy factor versus T with an accuracy comparable with that obtained by thermogravimetric measurements, routinely employed for this purpose. The evolution of the structural parameters (V, a, b, c, site occupancy factor of the template molecule) vs T has been obtained. These data allow us to have, for the first time, a complete view of the structural rearrangements induced by the template burning process on the zeolitic framework. The differences caused by the different heteroatom inserted in the MR lattice (Ti or Fe) are discussed. For both TS-1 and Fe-MFI, the kinetics of the reaction were investigated, to obtain the activation energy of the calcinations process employing the nonisothermal data according to the theory recently proposed by Kennedy and Clark [Thermochim. Acta, 1997, 307, 27-35]. For TS-1 only, the time-resolved template burning experiment has been repeated in isothermal conditions at four different temperatures, to obtain the activation energy from isothermal data, according to the standard procedure. Comparison between Arrhenius plots obtained from isothermal and nonisothermal data demonstrates that the Kennedy and Clark method can be also applied to complex materials such as the MFI zeolites. This approach, when applied to time-resolved XRPD studies, is much less time consuming (requesting, in principle, one single nonisothermal run) with respect to the classic approach, which requests at least three isothermal runs. Moreover, it allows a remarkably lower associated error (151 ±11 versus 146 ± 30 kJ mol[sup-1]) due to the much higher number of experimental points employed to perform the linear fit. [ABSTRACT FROM AUTHOR]

Examines the photochemistry of isomeric 3-furyliden- and benzylidenoxindoles (2H-indol-2-ones). Comparison of the results of a series of crystal structure analyses with those of the photochemical study; Application of the topochemical principle to the analysis of the crystal structures; Calculation of the interaction energies from the charge density study.

In materials and earth science, but also in chemistry, pharmaceutics and engineering, the quantification of elements and crystal phases in solid samples is often essential for a full characterization of materials. The most frequently used techniques for this purpose are X-ray fluorescence (XRF) for elemental analysis and X-ray powder diffraction (XRPD) for phase analysis. In both methods, relations between signal and quantity do exist but they are expressed in terms of complex equations including many parameters related to both sample and instruments, and the dependence on the active element or phase amounts to be determined is convoluted among those parameters. Often real-life samples hold relations not suitable for a direct quantification and, therefore, estimations based only on the values of the relative intensities are affected by large errors. Preferred orientation (PO) and microabsorption (MA) in XRPD cannot usually be avoided, and traditional corrections in Rietveld refinement, such as the Brindley MA correction, are not able, in general, to restore the correct phase quantification. In this work, a multivariate approach, where principal component analysis is exploited alone or combined with regression methods, is used on XRPD profiles collected on ad hoc designed mixtures to face and overcome the typical problems of traditional approaches. Moreover, the partial or no known crystal structure (PONKCS) method was tested on XRPD data, as an example of a hybrid approach between Rietveld and multivariate approaches, to correct for the MA effect. Particular attention is given to the comparison and selection of both method and pre-process, the two key steps for good performance when applying multivariate methods to obtain reliable quantitative estimations from XRPD data, especially when MA and PO are present. A similar approach was tested on XRF data to deal with matrix effects and compared with the more classical fundamental-parameter approach. Finally, useful indications to overcome the difficulties of the general user in managing the parameters for a successful application of multivariate approaches for XRPD and XRF data analysis are given. [ABSTRACT FROM AUTHOR]

A new soft and fast solid state reaction is exploited for the preparation of exchanged layered double hydroxide materials and, in particular, for intercalating bioactive molecules. The characterization of the nanocomposite, carried out by crystallographic and thermogravimetric techniques, revealed that this synthesis yield is comparable to that of standard methods but with time, solvent, and energy saving advantages. Moreover, the in situ diffraction experiments also allowed us to shed some light on the kinetics of the intercalation process. A new soft and fast solid state reaction is exploited for the preparation of exchanged layered double hydroxide materials and, in particular, for intercalating bioactive molecules. The synthesis yield by solvent-assisted grinding is comparable to that of standard methods but with time, solvent, and energy saving advantages. [ABSTRACT FROM AUTHOR]

The crystal structure of 4-methylcatechol (4MEC) has, to date, never been solved, despite its very simple chemical formula C7O2H8 and the many possible applications envisaged for this molecule. In this work, this gap is filled and the structure of 4MEC is obtained by combining X-ray powder diffraction and first principle calculations to carefully locate hydrogen atoms. Two molecules are present in the asymmetric unit. Hirshfeld analysis confirmed the reliability of the solved structure, since the two molecules show rather different environments and H-bond interactions of different directionality and strength. The packing is characterised by a peculiar hydrogen bond network with hydroxyl nests formed by two adjacent octagonal frameworks. It is noteworthy that the observed short contacts suggest strong inter-molecular interactions, further confirmed by strong inter-crystalline aggregation observed by microscopic images, indicating the growth, in many crystallization attempts, of single aggregates taller than half a centimetre and, often, with spherical shapes. These peculiarities are induced by the presence of methyl group in 4MEC, since the parent compound catechol, despite its chemical similarity, shows a standard layered packing alternating hydrophobic and polar layers. Finally, the complexity and peculiarity of the packing and crystal growth features explain why a single crystal could not be obtained for a standard structural analysis. [ABSTRACT FROM AUTHOR]

Noninvasive prenatal testing (NIPT) consists of determining fetal aneuploidies by quantifying copy number alteration from the sequencing of cell-free DNA (cfDNA) from maternal blood. Due to the presence of cfDNA of fetal origin in maternal blood, in silico approaches have been developed to accurately predict fetal aneuploidies. Although NIPT is becoming a new standard in prenatal screening of chromosomal abnormalities, there are no integrated pipelines available to allow rapid, accurate and standardized data analysis in any clinical setting. Several tools have been developed, however often optimized only for research purposes or requiring enormous amount of retrospective data, making hard their implementation in a clinical context. Furthermore, no guidelines have been provided on how to accomplish each step of the data analysis to achieve reliable results. Finally, there is no integrated pipeline to perform all steps of NIPT analysis. To address these needs, we tested several tools for performing NIPT data analysis. We provide extensive benchmark of tools performances but also guidelines for running them. We selected the best performing tools that we benchmarked and gathered them in a computational pipeline. NiPTUNE is an open source python package that includes methods for fetal fraction estimation, a novel method for accurate gender prediction, a principal component analysis based strategy for quality control and fetal aneuploidies prediction. NiPTUNE is constituted by seven modules allowing the user to run the entire pipeline or each module independently. Using two cohorts composed by 1439 samples with 31 confirmed aneuploidies, we demonstrated that NiPTUNE is a valuable resource for NIPT analysis. [ABSTRACT FROM AUTHOR]

Summary: In the last years, the quantity of data and the number of applications carried over web traffic have been continuously increasing and nowadays web browsing accounts for most of the Internet traffic. In such a scenario, a poor browsing experience can result very annoying to the end user, and the effective identification of the root cause of such bad performance is of primary interest to both the users and the network operators. In this paper, we present a unified framework, based on a novel lightweight open‐source publicly available probe and on an original statistical diagnosis algorithm, to correctly and effectively point out the segment of a web connection (eg, local client, backbone network, and DNS server) responsible for a poor web browsing experience. The extensive experimental evaluation carried out in the paper demonstrates the effectiveness of the proposed approach to diagnose poor quality of experience at a large scale. The quantity of data and applications carried over web traffic have been continuously increasing. In such a scenario, a poor browsing experience can result very annoying to the user and the effective identification of the root cause of such bad performance is of primary interest to both users and network operators. In this paper we present a unified framework to correctly and effectively point out the segment of a web connection responsible for a poor web browsing experience. [ABSTRACT FROM AUTHOR]

Nanocrystalline powders of monometallic and bimetallic imidazolates of Co, Zn and Ag were produced by a reaction carried out in water. The powders were characterized by powder X-ray diffraction and the crystal structures of the new compounds Ag2ZnIm4 and Ag2CoIm4 (Im = imidazolate) were solved. Heterometallic Co/Zn imidazolates showed the known Zn-zni crystal structure while Ag/Zn and Ag/Co systems were isostructural to the copper analogs. The powders were further characterized by EDX, UV-Vis and FTIR ATR spectroscopy in the solid state. The catalytic experiments indicated that out of the studied heterometallic compounds only Ag2Co(Im)4 exhibits some catalytic activity in the oxidation reaction of 1-phenylethanol with tert-butylhydroperoxide at elevated temperatures. [ABSTRACT FROM AUTHOR]

Obituary for Davide Viterbo [ABSTRACT FROM AUTHOR]

The article discusses the highlights of a workshop on the investigation of solid-state transformations and reactions at non-ambient conditions using simultaneous Raman-X-ray diffraction and absorption, held by the Swiss-Norwegian Beam Lines (SNBL) from June 18 to 19, 2008 in France. The use of such techniques in various studies in the fields of materials science, geophysics, sold state chemistry, among others, was demonstrated. Several of these studies were complex and carried under external stimuli so as to reproduce experiments on individual machines.

The cocrystallization of active pharmaceutical ingredient naproxen with some acridines (acridine, 9-aminoacridine, 6,9-diamino-2-ethoxyacridine) has been explored and the conditions under which the crystallization can be carried out have been investigated. While the crystallization of acridine-based molecular crystals was widely studied under solution conditions, solvent-free and/or mechanochemical method potentialities are still unknown. To fill this gap, the cocrystallization of naproxen with the above-mentioned acridines was attempted using different approaches, e.g., by heat treatment of the dry mechanical mixture and by liquid-assisted grinding (LAG), as alternatives to the traditional precipitation by a proper solution. In the first case, the reaction is driven under dry conditions by the temperature and gave no results independently of the temperature used, below or above the melting point of the reactants. In the second case, the reaction is driven by the mechanical action of grinding assisted by a few drops of solvent to facilitate and improve the reaction. This screening allowed obtaining three new molecular crystals for naproxen coupled to acridine and a mono-aminoacridine and solved by single-crystal and powder X-ray diffraction (PXRD). Two host–guest structures were obtained by solution crystallization, while a layered structure was obtained under LAG conditions. Interconversion between molecular crystals formed by the same chemical species was hindered once a molecular crystal was obtained by a specific technique. Hirshfeld and energy framework calculations confirmed the remarkable structural differences between 1α and 1β packing and suggested that 1β is kinetically more stable. Variable-temperature PXRD, DSC and TGA were used to explore the stability of the compounds. 6,9-Diamino-2-ethoxyacridine proved to be too polar and/or too bulky to form crystals with naproxen regardless of the preparation method and the different stoichiometric ratios used. It is noteworthy that LAG allowed the preparation of the naproxen/acridine molecular crystal with a yield higher than 99% under almost solvent-free conditions. DSC indicated the formation of a eutectic between naproxen and acridine, with the possibility of recrystallizing the 1 : 1 complex also from the melt solution. [ABSTRACT FROM AUTHOR]

The silicon-sulfur compound bis-1,3-[di(2,6-diisopropylphenoxy)]disiloxane-1,3-dithiol was obtained from silicon disulfide and 2,6-diisopropylphenol in a reaction catalyzed by imidazole or 4-(dimethylamino)pyridine (DMAP). The disiloxane-1,3-dithiol is produced in a low yield but in a repeatable manner and can be isolated as colorless crystals. The X-ray crystal structure of the compound reveals a linear or close-to-linear Si-O-Si angle and a mutual trans position of the two hydrosulfido groups. The compound forms a chelating mononuclear complex with cadmium ions. In the complex, the sulfido groups adopt a cis conformation, and the Si-O-Siangle deviates from linearity. The molecular structure of the compound is discussed on the basis of DFT calculations. [ABSTRACT FROM AUTHOR]

Organo-modified layered materials characterization poses challenges due to their complexity and how other aspects such as contamination, preparation methods and degree of intercalation influence the properties of these materials. Consequently, a deep understanding of their interlayer organization is of utmost importance to optimize their applications. These materials can in fact improve the stability of photoactive molecules through intercalation, avoiding the quenching of their emission at the solid state, to facilitate their use in sensors or other devices. Two synthetic methods for the preparation of saponites with a cationic surfactant (CTABr) and a neutral chromophore (Fluorene) were tested and the obtained products were initially characterized with several complementary techniques (XRPD, SEM, TGA, IR, UV-Vis, Fluorescence and Raman spectroscopy), but a clear understanding of the organization of the guest molecules in the material could not be obtained by these techniques alone. This information was obtained only by thermogravimetry coupled with gas chromatography and mass spectroscopy (TGA-GC-MS) which allowed identifying the species present in the sample and the kind of interaction with the host by distinguishing between intercalated and adsorbed on the surface. [ABSTRACT FROM AUTHOR]

The heating process (30–200 °C) of a palygorskite-indigo mixture has been monitored in situ and simultaneously by synchrotron powder diffraction and Raman spectroscopy. During this process, the dye and the clay interact to form Maya blue (MB), a pigment highly resistant to degradation. It is shown that the formation of a very stable pigment occurs in the 70–130 °C interval; i.e., when palygorskite starts to loose zeolitic water, and is accompanied by a reduction of the crystallographic a parameter, as well as by alterations in the C=C and C=O bonds of indigo. Mid- and near-infrared spectroscopic work and microporosity measurements, employed to study the rehydration process after the complex formation, provide evidence for the inhibition of the rehydration of MB as compared with palygorskite. These results are consistent with the blocking of the palygorskite tunnel entrance by indigo molecules with a possible partial penetration inside the tunnels. The surface silanols of palygorskite are not perturbed by indigo, suggesting that MB is not a surface complex. [ABSTRACT FROM AUTHOR]

Plasticized–Poly(vinyl chloride) (P-PVC) for cables and insulation requires performances related to outdoor, indoor and submarine contexts and reduction of noxious release of HCl-containing fumes in case of thermal degradation or fire. Introducing suitable nanomaterials in polymer-based nanocomposites can be an answer to this clue. In this work, an industry-compliant cable-grade P-PVC formulation was added with nanostructured materials belonging to the family of Polyhedral Oligomeric Silsesquioxane (POSS). The effects of the nanomaterials, alone and in synergy with HCl scavenging agents as zeolites and hydrotalcites, on the thermal stability and HCl evolution of P-PVC were deeply investigated by thermogravimetric analysis and reference ASTM methods. Moreover, hardness and mechanical properties were studied in order to highlight the effects of these additives in the perspective of final industrial uses. The data demonstrated relevant improvements in the thermal stability of the samples added with nanomaterials, already with concentrations of POSS down to 0.31 phr and interesting additive effects of POSS with zeolites and hydrotalcites for HCl release reduction without losing mechanical performances. [ABSTRACT FROM AUTHOR]

The exact recipe to prepare the ancient Maya Blue (MB), an incredibly resistant and brilliant pigment prepared from indigo (dye) and Palygorskite (clay), is lost to the ages. To unravel the key features of the MB formation process, several inorganic‐dye couples were heated to 200 °C and cooled to RT, to investigate their reactivity and the diffusion and degree of sequestration of the dye into the inorganic host. In situ XRPD/PDF and fiber optic reflectance spectroscopy (FORS) data, along with TGA, provided a comprehensive overview on MB formation mechanism. XRPD/PDF gave information on long/short range behaviors of water desorption/adsorption and indigo sequestration, while TGA and in situ FORS gave information on mass and optical changes within temperature. Ex situ dye removal was used to understand the sample stability after the thermal treatment. A statistical approach based on principal component analysis was exploited to efficiently and jointly analyze the ≈3000 collected patterns. MB formation starts below 110 °C with disordered distribution of indigo within the channels, reaching maximum reaction speed and higher ordering at 150 °C. Above 175 °C, color changes and a stronger sequestration of indigo into framework channels are observed, whereas the affinity for water is dramatically reduced. The origin of different colors, hues, and stability in historical MB samples can then be explained in terms of different thermal histories of the starting mechanical indigo/palygorskite mixtures. [ABSTRACT FROM AUTHOR]

The increasing efficiency of detectors and brightness of X‐rays in both laboratory and large‐scale facilities allow the collection of full single‐crystal X‐ray data sets within minutes. The analysis of these 'crystallographic big data' requires new tools and approaches. To answer these needs, the use of principal component analysis (PCA) is proposed to improve the efficiency and speed of the analysis. Potentialities and limitations of PCA were investigated using single‐crystal X‐ray diffraction (XRD) data collected in situ on Y zeolite, in which CO2, acting as an active species, is thermally adsorbed while cooling from 300 to 200 K. For the first time, thanks to the high sensitivity of single‐crystal XRD, it was possible to determine the sites where CO2 is adsorbed, the increase in their occupancy while the temperature is decreased, and the correlated motion of active species, i.e. CO2, H2O and Na+. PCA allowed identification and elimination of problematic data sets, and better understanding of the trends of the occupancies of CO2, Na+ and water. The quality of the data allowed for the first time calculation of the enthalpy (ΔH) and entropy (ΔS) of the CO2 adsorption by applying the van 't Hoff equation to in situ single‐crystal data. The calculation of thermodynamic values was carried out by both traditional and PCA‐based approaches, producing comparable results. The obtained ΔH value is significant and involves systems (CO2 and Y zeolite) with no toxicity, superb stability and chemical inertness. Such features, coupled with the absence of carbonate formation and framework inertness upon adsorption, were demonstrated for the bulk crystal by the single‐crystal experiment, and suggest that the phenomenon can be easily reversed for a large number of cycles, with CO2 released on demand. The main advantages of PCA‐assisted analysis reside in its speed and in the possibility of it being applied directly to raw data, possibly as an 'online' data‐quality test during data collection, without any a priori knowledge of the crystal structure. In situ single‐crystal X‐ray diffraction data were used to unravel the structural dynamics and enthalpy and entropy of adsorption of CO2 into Y zeolite. A principal‐component‐analysis‐ (PCA) based approach is applied in an innovative way to single‐crystal X‐ray diffraction data analysis, allowing one to selectively detect the information from the subset of active atoms. The potential of and limitations of PCA in single‐crystal diffraction are discussed. [ABSTRACT FROM AUTHOR]

The GdIII-complexes of DO3A-acetophenone and ortho- or para- hydroxyacetophenone ligands have been investigated to assess the effect of the presence of a phenol group on the relaxivity and on the water exchange rate of these potential MRI contrast agents. H-Bonding between the ortho-phenol(ate) groups and the water molecules involved in the dissociative exchange mechanism is shown to speed up the water exchange rate by stabilizing the eight-coordinate transition state. [ABSTRACT FROM AUTHOR]

Hydrotalcites are layered double hydroxides (LDHs) of the anionic clay family. They can be obtained by synthesis, with high purity and controlled stoichiometry but with much larger preparation efforts and costs with respect to natural ores. Their properties can be tailored by changing the metals of the layer, or by inserting proper inorganic or organic anions. The reason of the few industrial applications of LDHs might be the difficulty of scaling up their synthesis and anion exchange methods, requiring often cumbersome procedures for filtering, recovery and purification of the final products. Recently, huge efforts were made to obtain facile and easily scalable preparation methods, especially favoured by the almost complete elimination of solvents and water-based procedures. The structures of the nanocomposites were studied by several techniques, from electron microscopy and diffraction to X-ray powder diffraction (the unique structural techniques able to face the low crystallinity of these materials) coupled with others, to obtain an exhaustive view of LDHs structure and reactivity. These advancements and the perspectives of larger LDHs industrial applications are described. [ABSTRACT FROM AUTHOR]

Pidotimod ® is a dipeptide with widely recognized immunomodulatory properties and with particularly beneficial effects for the treatment of acute respiratory and urinary tract infections. Pidotimod ® presents two chiral centres which originate four stereoisomers. ( 4R,2′S , 4S,2′R , 4R,2′R and 4S,2′S ). To date, only the 4R,2′S and 4S,2′R stereoisomers are reported in the literature. We report here the absolute crystal structure of the 4R,2′R and 4S,2′S diastereoisomers of Pidotimod ® , obtained by crystals grown by slow evaporation of a mixture of water and ethanol. The analysis of the crystal structures revealed the key role of a solvent water molecule in the crystal packing engaged in an extended hydrogen bonds network. This water-assisted H-bond network explained the recalcitrance of 4R,2′R and 4S,2′S Pidotimod ® to crystallize in pure ethanol, despite their high solubility, and the growth of well-diffracting crystals only in presence of water. Hence, Pidotimod ® 4R,2′R and 4S,2′S stereoisomers markedly differ from the 4R,2′S and 4S,2′R ones, which crystallize in absence of water. The molecular and crystal structures of the 4R,2′R and 4S,2′S Pidotimod ® stereoisomers here presented gave some hints on the differences in bioactivity with respect to the 4R,2′S stereoisomer. In fact, beyond an expected different dispositions of hydrophilic ligands, 4R,2′R and 4S,2′S showed an incremented tendency to intermolecular H-bonds with water. [ABSTRACT FROM AUTHOR]

Magnesium alloys in general, and AZ31 in particular, have huge potential as materials for energy saving and emissions reduction in the transportation of people and goods, because of their low density (about 1.7 g∙cm−3) coupled to good bulk mechanical properties. The main weakness is represented by the alloy surface, prone to corrosion and rather soft. Coatings are therefore mandatory, especially in harsh environments. To obtain AZ31 materials with exceptional surface properties High Velocity Oxygen-Fuel (HVOF) thermal spray was exploited to deposit a WC-CoCr coating with very high surface hardness. Because of the heat sensitivity of magnesium alloys, the influence of torch-substrate kinematics and substrate surface preparation on the surface temperature during deposition, the metallurgical characteristics of AZ31, and the residual stress state of the coated samples were investigated. The overall quality of the coatings was also evaluated by abrasion and electrochemical corrosion resistance tests. Proper adjustment of the torch/substrate standoff distance and torch patterning strategy reduced the surface temperature during deposition by around 100 °C, as measured with an IR pyrometer. This also resulted in a decreased magnitude of the average compressive stress in the coating. At the same time, these adjustments did not impair measurably the performances of the coatings, which, regardless of the deposition conditions, had approximately 1200 HV 0.3 hardness, 2–4 μA∙cm−2 corrosion current density in 3.5 wt./vol% NaCl aqueous solution, and 7–8 × 10−4 mm3∙(N∙m)−1 specific wear rate under dry particles' abrasion conditions. Cyclic impact tests also showed that the coatings adhered equally well to grit-blasted or machined surfaces. On the other hand, transverse cracks developed across the coatings during impact tests because of the much higher elastic and plastic deformability of the AZ31 substrate. The avoidance of grit-blasting and the lowered deposition temperatures were also important to prevent anomalous grain growth in the AZ31 substrate. [Display omitted] • Stand-off distance and torch/substrate kinematics controlled the deposition temperature. • The compressive stress level in the coating depended on the deposition temperature. • High deposition temperature caused anomalous grain growth in grit-blasted AZ31. • HVOF-sprayed WC-CoCr particles penetrated deep into the AZ31 substrate. • Thus, grit-blasting was not needed to achieve sound coating/substrate adhesion. [ABSTRACT FROM AUTHOR]

This work provides the synthesis, structural characterization, electrochemical and photophysical features, as well as the application in light-emitting electrochemical cells (LECs) of a novel heteroleptic copper(i) complex – [Cu(impy)(POP)][PF6], where impy is 3-(2-methoxyphenyl)-1-(pyridine-2-yl)imidazo[1,5-a]pyridine and POP is bis{2-(diphenylphosphanyl)phenyl}ether. This compound shows blue photoluminescence (PL, λ = 450 nm) in solution and solid-state and excellent redox stability. Despite these excellent features, the electroluminescence (EL) response is located at ∼550 nm. Although the EL spectrum of LECs is typically red-shifted compared to the PL of the electroluminescent material, a shift of ca. 100 nm represents the largest one reported in LECs. To date, the large shift phenomena have been attributed to (i) a change in the nature of the lowest emitting state due to a concentration effect of the films, (ii) a reversible substitution of the ligands due to the weak coordination to the Cu(i), and (iii) a change in the distribution of the excited states due to polarization effects. After having discarded these along with others like the irreversible degradation of the emitter during device fabrication and/or under operation conditions, driving conditions, active layer composition, and changes in the excited states under different external electrical stimuli, we attribute the origin of this unexpected shift to a lack of a thermally activated delayed fluorescence (TADF) process due to the solely ligand-centered character of the excited states. As such, the lack of a charge transfer character in the excited states leads to a blue-fluorescence and yellow-phosphorescence photo- and electro-responses, respectively. This corroborates recent studies focused on the design of TADF for heteroleptic copper(i) complexes. Overall, this work is a clear insight into the design of new copper(i) complexes towards the preparation of blue LECs, which are still unexplored. [ABSTRACT FROM AUTHOR]

The synthesis, the NMR characterization and the crystal structure of 6-Chloro 4,4′-dimethyl 2,2′-bipyridine and of the reaction intermediate 4,4′-Dimethyl 2,2′-bipyridine N-Oxide are here reported. The target compound crystallizes in the orthorhombic system while the intermediate is monoclinic. In both structures, the molecules are linked by weak interactions. The structure of the reaction intermediate N-oxide is characterized by a dihedral angle between the two phenyl rings of 161.77° while the other is almost planar with a dihedral angle of 179.15°. The crystal packing was investigated, also with the aid of Hirshfeld surface analysis. In the N-oxide reaction intermediate the packing is governed by CH–O interactions, while in the product the packing is simply driven by minimizing the voids and thus maximizing the density, with a prevalence of H•••H and C•••H contacts, as indicated by fingerprint decomposition analysis. [ABSTRACT FROM AUTHOR]

The cover picture shows the electronic structure and simplified formula of the complicated derivative of orthothiosilicic acid: bis‐1,3‐[bis(2,6‐diisopropylphenoxy)]disiloxane‐1,3‐dithiol. The compound is relatively stable as a result of the kinetic protection of hydrophobic dipp (diisopropylphenyl) substituents and can therefore be utilized as ligand in the synthesis of chelating metal complexes. In the background, one can see large deposits of another silicon compound, namely silicon dioxide (silica, quartz). These deposits, popularly called beaches, are especially wide and beautiful along the Baltic Sea near Gdańsk and were photographed by the corresponding author during a walk with her children on August 5, 2006. Details are discussed in the article by A. Dołęga, E. Conterosito et al. on p. 3059 ff. For more on the story behind the cover research, see the Cover Profile. [ABSTRACT FROM AUTHOR]

Invited for the cover of this issue is the group of Anna Dołęga at the Gdansk University of Technology, Poland. The cover image shows the electronic structure and simplified formula of bis-1,3-[bis(2,6-diisopropylphenoxy)]disiloxane-1,3-dithiol, a suitable ligand for the synthesis of chelating metal complexes, against a background of a more popular compound of silicon, sand. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) are versatile materials used for intercalating bioactive molecules in the fields of pharmaceuticals, nutraceuticals and cosmetics, with the purpose of protecting them from degradation, enhancing their water solubility to increase bioavailability and improving their pharmacokinetic properties and formulation stability. Moreover, LDHs are used in various technological applications to improve stability and processability. The crystal chemistry of hydrotalcite-like compounds was investigated by X-ray powder diffraction (XRPD), automated electron diffraction tomography (ADT) and thermogravimetric analysis (TGA)-GC-MS to shed light on the mechanisms involved in ion exchange and absorption of contaminants, mainly carbonate anions. For the first time, ADT allowed a structural model of LDH_NO3 to be obtained from experiment, shedding light on the conformation of nitrate inside LDH and on the loss of crystallinity due to the layer morphology. The ADT analysis of a hybrid LDH sample (LDH_EUS) clearly revealed an increase in defectivity in this material. XRPD demonstrated that the presence of carbonate can influence the intercalation of organic molecules into LDH, since CO3-contaminated samples tend to adopt d spacings that are approximate multiples of the d spacing of LDH_CO3. TGA-GC-MS allowed intercalated and surface- adsorbed organic molecules to be distinguished and quantified, the presence and amount of carbonate to be confirmed, especially at low concentrations (<2 wt %), and the different types and strengths of adsorption to be classified with respect to the temperature of elimination. [ABSTRACT FROM AUTHOR]

• three polymorphic couples, a couple of pseudo polymorphs and a protonated structure of imidazo[1-5a]pyridine based chromophores have been crystallized. • Z'>1 tendency, solvated crystal form and non-centrosymmetric structure appearance are reported. • First comprehensive Raman-Ir characterization and assignation have been done. [Display omitted] The polymorphism and solid-state peculiarities of imidazo[1,5- a ]pyridine derivatives have been investigated by a theoretical and experimental approach to shed light on the structural and energetic features. Four couples of polymorphs and an ionic crystal form have been reported and analysed. Hirshfeld Surface and Energy Frameworks have been used to better understand the crystal packing features, in comparison with literature structures. The collection of these characterizations made possible to analyze the differences between the polymorphs, the energetic components dominating the crystal packing, and the effect of the different substitutions on the central molecular skeleton on packing disposition. To complete the solid state characterization of the molecular products, the assignment of vibrational spectra for the imidazo[1,5- a ]pyridine core derivatives has been performed for the first time and the influence of substituents commented. Although the discussed polymorphs are very different in their crystal packing, from the energetic point of view they present a strong similarity. In all cases, the main interactions are π‧‧‧π stacking and C-H‧‧‧π to the aromatic rings, with some tendency to the formation of C-H‧‧‧N contacts to the central imidazo[1,5- a ]pyridine nitrogen. The main energetic component is the dispersive one, with some contribution from the electrostatic component, and this situation is not modified by the presence of differing substituents. When hydrogen bond are present, the crystal packing is strongly modified and, energetically, the electrostatic component can overcome the dispersive one. [ABSTRACT FROM AUTHOR]

A new mechanochemical method for the fast and clean preparationof exchanged layered double hydroxides (LDHs) was designed and testedon compounds with different chemical features, to assess its feasibilityand applicability, to optimize yields and reaction speeds, and toidentify its potential and limitations. Thanks to the simplicity andspeed of the proposed method, we were able to upscale the method andproduce several hundreds of grams of exchanged hydrotalcite. Moreover,fast in situX-ray powder diffraction measurements,performed using synchrotron radiation, allowed us to unravel the mechanismand kinetics of the process. This showed that it is possible to carryout the complete reaction in less than 1000 s instead of days. Thechosen organic guests were 3-carboxy coumarin and, given their importance,a series of nonsteroidal anti-inflammatory drugs with different pKavalues and steric hindrance, namely, ketoprofen,flurbiprofen, ibuprofen, indomethacin, and tiaprofenic acid. The methodhas been applied to different classes of compounds to characterizethe reaction in terms of speed, yield, and applicability. The characterizationof the obtained nanocomposites, carried out by crystallographic andmicroscopic techniques, revealed that the synthesis yields are comparableto that of standard methods, but with enormous time, solvent, andenergy saving advantages. Moreover, in situdiffractionexperiments allowed us to shed some light on the kinetics of the intercalationprocess with subsecond resolution and to determine the parametersaffecting the reaction. Steric hindrance of the molecule proved tobe the most relevant parameter to determine the applicability of thismethod. [ABSTRACT FROM AUTHOR]

This paper describes a new method for extracting the individual contributions to the diffracted intensity of subsets of atoms in the crystal structure. The periodic perturbation of the scattering process, required for untangling the scattered intensity, is provided by altering the resonant contributions. The theory of modulation enhanced diffraction (MED) is briefly recalled in the context of resonant scattering. A periodic variation in the atomic form factor has been achieved by changing the X-ray energy in such a way that the MED theory holds. Simulated results and experimental data are presented, together with necessary corrections. Two data analysis schemes are presented, both illustrating the advantages and drawbacks of the novel modulation technique. [ABSTRACT FROM AUTHOR]

Modulation excitation spectroscopy is a powerful and well established technique for investigating the dynamic behaviour of chemical and physical systems. Recently, an expansion of this technique for diffraction was proposed and the theory deriving the diffraction response of a crystal subjected to a periodically varying external perturbation was developed [Chernyshov, van Beek, Emerich, Milanesio, Urakawa, Viterbo, Palin & Caliandro (2011). Acta Cryst. A 67, 327-335]. The result of this is that a substructure composed of atoms actively responding to the stimulus may be separated out by analysing the diffraction signal at a frequency twice that of the stimulus. This technique is called modulation-enhanced diffraction. Here, a version of the theory dealing with the modulation of the site occupancies of a selected subset of atoms is formulated, and this is supported by experiments carried out at the Swiss-Norwegian Beam Lines at the ESRF, involving periodic variation of the xenon content of a polycrystalline zeolite as a function of temperature. The data analysis involves three steps: (i) data selection is carried out to mimic a linear response; (ii) phase-sensitive detection is applied to obtain contributions both from the responding part of the electron density associated with the Xe atoms and from the interference term; (iii) a phasing procedure is applied to both. A Patterson deconvolution technique has been successfully used to phase the demodulated diffraction patterns and obtain the active substructure. [ABSTRACT FROM AUTHOR]

Typical hydrogen-bonded cobaltocinium salts of formula [Cp2Co+][A−] [with Cp = C5H5 and A = PF6 ( 1), AsF6 ( 2), SbF6 ( 3), I ( 4), I3 ( 5), Co(CN)6 ( 6), Co(CO)4 ( 7), Br3 ( 8), FeI4 ( 9) and HCl2 ( 10)] were studied by means of a combined structural, spectroscopic (IR, Raman, solid-state NMR) and theoretical approach. The solid-state vibrational spectra show blue or red shift hydrogen bond behavior depending on the anionic species, i.e. high- or low-frequency ν(CH) shift with respect to the solution value. The crystal structure of the new complex [Cp2Co+][SbF6−], a blue-shifted system, is reported while the [Cp2Co+][I−] complex, a red-shifted system disordered at room temperature, reveals a novel ordered polymorph at 150 K. The weak interactions (C…H, H…H, H…X, C…X) between cations and anions were analyzed by means of the Hirshfeld surfaces model, which permits their clear graphic visualization. HS fingerprint plots and normalized contact distances visually describe the difference between blue- and red-shifted complexes. Chemical shift tensors and shielding anisotropy values of the Cp carbon atoms, extracted from 13C CPMAS solid-state NMR spectra, allow the evaluation of Cp rotational motions which are related to the intermolecular contact extent. Finally, a DFT computational model is able to rationalize all the experimental data. It shows that the prevalence of one between two forces, that is, the attractive polarization of C–H bonds and the repulsive effect of electronic clouds, leads to the blue or red shift phenomenon. [ABSTRACT FROM AUTHOR]

The article presents a study which develops a theory to identify the kinematic diffraction response to a periodic perturbation of a crystal. It shows that the diffracted signal doubles the function of the stimulation frequency when a part of a local electron density varies linearly with an external stimulus. It discusses two ways of filtering, demodulation and correlation, with respect to extracting information from the experiment.

Dealumination of NH4-Y zeolite during steaming to 873 K was investigated with in situ, time-dependent, synchrotron radiation XRPD and in situ Al K-edge XAS. Water desorption is complete at 450 K, and ammonium decomposition occurs between 500 and 550 K. Only a small fraction of Al3+ species (5%) leaves the framework during heating from 710 to 873 K; these species occupy site I' inside the sodalite cage. This fraction increases up to 8% in the first 50 mm at 873 K and remains constant for the following 70 mm isotherm and during the high-temperature part of the cooling experiment. During cooling from 500 to 450 K, the electron density at site I' increases suddenly, corresponding to a fraction of 30-35% of the total Al, confirmed by ex situ 27Al MAS solid-state NMR. At that temperature, in situ Al K-edge XAS indicates a change in Al coordination of a large fraction of Al, and thermogravimetric (TG) data show the first water molecules start to repopulate the pores. Such molecules drive the dislodgment of most of the Al from the zeolitic framework. Our data indicate that considerable structural collapse caused by steaming does not occur at the highest temperature; however, defects form, which lead to significant migration of framework Al3+ to extraframework positions, which occurs only as water is able to enter the pores again, that is, at much lower temperature. Contrary to general opinion, these results demonstrate that zeolite dealumination is not primarily a high-temperature process. The standard Rietveld refinement approach failed to identify extraframework Al species. These new results were obtained by adopting the innovative parametric refinement [J. Appl. Crystallogr. 2007, 40, 87]. Treating all of the XRPD patterns collected during the evolution of temperature as one unique data set significantly reduces the overall number of optimized variables and, thus, their relative correlation, and finally results in a more reliable estimate of the optimized parameters. Our results contribute to a better understanding of the phenomena involved on the atomic scale in the preparation of ultrastable Y zeolites (USY). USY are employed in fluid catalytic cracking (FCC), which is the most important conversion process in petroleum refineries to convert the high-boiling hydrocarbon fractions of petroleum crude oils to more valuable products like gasoline and olefinic gases. [ABSTRACT FROM AUTHOR]

X-ray powder diffraction played a key role in materials science over the past 25 years. It is now possible to employ powder diffraction at in situ conditions to study solid-state transformations. “Real” materials science samples often show deviations from the “perfectly crystalline” state and hence powder diffraction reaches its limits. Spectroscopic techniques can often provide useful complementary information. With the aim of gaining information from this aspect, we combined Raman spectroscopy with diffraction. A novel experimental setup for simultaneous in situ Raman and XRPD experiments was designed and realized at the SNBL line at ESRF Synchrotron (Grenoble-F). High-resolution XRPD data can be collected with a time resolution in the range of minutes. A permanently installed Raman spectrometer can now be used to measure the same sample at the same spot under the same conditions. A wide variety of non-ambient conditions are available. The setup is described with limitations and potentialities, by describing one example of application. Finally some hints on future improvements are described. [ABSTRACT FROM AUTHOR]

Materials containing disordered moieties and/or amorphous or liquid-like phases or showing surface- or defect-related phenomena constitute a problem with respect to their characterization using X-ray powder diffraction (XRPD), and in many cases Raman spectroscopy can provide useful complementary information. A novel experimental setup has been designed and realized for simultaneous in situ Raman/high-resolution XRPD experiments, to take full advantage of the complementarities of the two techniques in investigating solid-state transformations under non-ambient conditions. The added value of the proposed experiment is the perfect synchronization of the two probes with the reaction coordinate and the elimination of possible bias caused by different sample holders and conditioning modes used in ` in situ but separate' approaches. The setup was tested on three solid-state transformations: (i) the kinetics of the fluorene–TCNQ solid-state synthesis, (ii) the thermal swelling and degradation of stearate–hydrotalcite, and (iii) the photoinduced (2 + 2)-cyclization of ( E)-furylidenoxindole. These experiments demonstrated that, even though the simultaneous Raman/XRPD experiment is more challenging than separate procedures, high-resolution XRPD and Raman data can be collected. A gas blower allows studies from room temperature to 700 K, and 100 K can be reached using a nitrogen cryostream. The flexibility of the experimental setup allows the addition of ancillary devices, such as a UV lamp used to study photoreactivity. [ABSTRACT FROM AUTHOR]

Abstract: We report a combined experimental and computational study of new rhenium tricarbonyl complexes based on the bidentate heterocyclic N–N ligands 2-(4-methylpyridin-2-yl)benzo[d]-X-azole (X=N–CH3, O, or S) and 2-(benzo[d]-X-azol-2-yl)-4-methylquinoline (X=N–CH3, O, or S). Two sets of complexes are reported. Chloro complexes, described by the general formula Re(CO)3[2-(4-methylpyridin-2-yl)benzo[d]-X-azole]Cl (X=N–CH3, 1; X=O, 2; X=S, 3) and Re(CO)3[2-(benzo[d]-X-azol-2-yl)-4-methylquinoline]Cl (X=N–CH3, 4; X=O, 5; X=S, 6) were synthesized heating at reflux Re(CO)5Cl with the appropriate N–N ligand in toluene. The corresponding pyridine set {Re(CO)3[2-(4-methylpyridin-2-yl)benzo-X-azole]py}PF6 (X=N–CH3, 7; X=O, 8; X=S, 9) and {Re(CO)3[2-(benzo[d]-X-azol-2-yl)-4-methylquinoline]py}PF6 (X=N–CH3, 10; X=O, 11; X=S, 12) was synthesized by halide abstraction with silver nitrate of 1–6 followed by heating in pyridine and isolated as their hexafluorophosphate salts. All complexes have been fully characterized by IR, NMR, electrochemical techniques and luminescence. The crystal structures of 1 and 7 were obtained by X-ray diffraction. DFT and time-dependent (TD) DFT calculations were carried out for investigating the effect of the organic ligand on the optical properties and electronic structure of the reported complexes. [Copyright &y& Elsevier]

A series of himbacine (1)-related analogues has been prepared featuring three different isomeric configurations with respect to the B-ring (a, b and natural c) and three different interconnecting two-carbon unsaturated units [natural (E)-ene, (Z)-ene, and yne]. The study of the binding affinities of the nine resulting compounds, including synthetic (+)-himbacine (3c), towards the M1–M4 muscarine receptor subtypes revealed that analogues 3a and 5c display a promising 10-fold selectivity for the M2 receptor as compared to the M1 receptor. [Copyright &y& Elsevier]

The reaction of amine ligands with the unsaturated 46 e− cluster Os3(μ-H2)(CO)10 yields a series of complexes of formula Os3H(μ-H)(CO)10(amine). In these derivatives the presence of an unconventional hydrogen-bond M&z.sbnd;H⋯H&z.sbnd;N is detected by the evaluation of proton spin-lattice relaxation times. In order to elucidate the relationship between pKb and H⋯H length, the M&z.sbnd;H⋯H&z.sbnd;N distances were quantified for amines of known pKb. In practice, this was achieved by comparing the T1 values of the terminal hydride resonances of the protonated isotopomer with the T1 values of the corresponding derivative containing selectively deuterated amine. A nice correlation between the M&z.sbnd;H⋯H&z.sbnd;N distances and the pKb of the amine ligands was found. DFT calculations were carried out for the cluster on Os3H(μ-H)(CO)10(Benzylamine) to gain a fuller understanding of the possible coordination geometries of an amine ligand on the surface of a tri-osmium cluster. [Copyright &y& Elsevier]

Low-cost, environmentally friendly and easily applicable coating for Mg alloys, able to resist in real world conditions, are studied. Coatings already used for other metals (aluminum, steel) and never tested on Mg alloy for its different surface and reactivity were deposited on AM60 magnesium alloys to facilitate their technological applications, also in presence of chemically aggressive conditions. A biobased PA11 powder coating was compared to synthetic silicon-based and polyester coatings, producing lab scale samples, probed by drop deposition tests and dipping in increasingly aggressive, salty, basic and acid solutions, at RT and at higher temperatures. Coatings were analyzed by SEM/EDX to assess their morphology and compositions, by optical and IR-ATR microscopy analyses, before and after the drop tests. Migration analyses from the samples were performed by immersion tests using food simulants followed by ICP-OES analysis of the recovered simulant to explore applications also in the food contact field. A 30 μm thick white lacquer and a 120 μm PA11 coating resulted the best solutions. The thinner siliconic and lacquer coatings, appearing brittle and thin in the SEM analysis, failed some drop and/or dipping test, with damages especially at the edges. The larger thickness is thus the unique solution for edgy or pointy samples. Finally, coffee cups in AM60 alloy were produced, as real word prototypes, with the best performing coatings and tested for both migration by dipping, simulating also real world aging (2 h in acetic acid at 70° and 24 h in hot coffee at 60 °C): PA11 resulted stable in all the tests and no migration of toxic metals was observed, resulting a promising candidate for many real world application in chemically aggressive environments and also food and beverage related applications. [ABSTRACT FROM AUTHOR]

Composite lightweight materials for X-ray shielding applications were studied and developed with the goal of replacing traditional screens made of lead and steel, with innovative materials with similar shielding properties, but lighter, more easily formed and workable, with lower impact on the environment and reduced toxicity for human health. New epoxy based composites additivated with barium sulfate and bismuth oxide were designed through simulations performed with softwares based on Geant4. Then, they were prepared and characterized using different techniques starting from digital radiography in order to test the radiopacity of the composites, in comparison with traditional materials. The lower environmental impact and toxicity of these innovative screens were quantified by Life Cycle Assessment (LCA) calculation based on the ecoinvent database, within the openLCA framework. Optimized mixtures are (i) 20% epoxy/60% bismuth oxide/20% barite, which guarantees the best performance in X-ray shielding, largely overcoming steel, but higher in costs and a weight reduction of circa 60%; (ii) 20% epoxy/40% bismuth oxide/40% barite which has slightly lower performances in shielding, but it is lighter and cheaper than the first one and (iii) the 20% epoxy/20% bismuth oxide/60% barite which is the cheapest material, still maintaining the X-ray shielding of steel. Depending on cost/efficiency request of the specific application (industrial radiography, aerospace, medical analysis), the final user can choose among the proposed solutions. [ABSTRACT FROM AUTHOR]

Low-ordered carbon/layered double hydroxide (LDH) nanocomposites were prepared by rehydration of the oxides produced by calcination of an organic LDH. While the memory effect is a widely recognized effect on oxides produced by inorganic LDH, it is unprecedented from the calcination/rehydration of organic ones. Different temperatures (400, 600, and 1100 °C) were tested on the basis of thermogravimetric data. Water, instead of a carbonate solution, was used for the rehydration, with CO2 available from water itself and/or air to induce a slower process with an easier and better intercalation of the carbonaceous species. The samples were characterized by X-ray powder diffraction (XRPD), infrared in reflection mode (IR), and Raman spectroscopies and scanning electron microscopy (SEM). XRPD indicated the presence of carbonate LDH, and of residuals of unreacted oxides. IR confirmed that the prevailing anion is carbonate, coming from the water used for the rehydration and/or air. Raman data indicated the presence of low-ordered carbonaceous species moieties and SEM and XRPD the absence of separated bulky graphitic sheets, suggesting an intimate mixing of the low ordered carbonaceous phase with reconstructed LDH. Organic LDH gave better memory effect after calcination at 400 °C. Conversely, the carbonaceous species are observed after rehydration of the sample calcined at 600 °C with a reduced memory effect, demonstrating the interference of the carbonaceous phase with LDH reconstruction and the bonding with LDH layers to form a low-ordered carbon/LDH nanocomposite. [ABSTRACT FROM AUTHOR]